Errors are the most deceiving way to measure defense. They are subject to all kinds of things outside the control of the player, not the least of which is the official scorer. Minor league field conditions also play a part. But, more than anything, guys who commit a lot of errors also end to lead their leagues in chances, as Santana did last year.
To give you a little context, Greg Gagne had 39 errors in AA in in 1982 and 34 errors in 1983. Yet, he's widely regarded as the best defensive shortstop in Twins history.
Gagne was 20 years old when he was in AA, Santana was 23.
If you look at fielding percentage, Santana was at .943 last year. Florimon was at .973 in the majors and Stephen Drew was at .984.
I am guessing .943 lands you about last in the MLB, this list only goes to 20. Some may find it unfair to compare a 23 year old to major leaguers, but I am guessing the balls come at the SS a lot faster in the big leagues.